Chapter 5 - Work and Energy - Learning Path Questions and Exercises - Exercises - Page 176: 41

a). $0.16J$ b). $0.32J$

a). $F=k\Delta x$ $mg=k\Delta x$ $\Delta x=\frac{mg}{k}=\frac{0.5\times9.8}{75}=0.065m$ Change in spring potential energy =$\frac{1}{2}kx^{2}=0.16J$ b). Initially spring is at free state and mass at x=0. Initial gravitational potential energy = 0. So, change in gravitational potential energy =$-mgh=-0.32J$ Taking the absolute value, change $=0.32J$